Fixation of polypropylene fibers impregnated with dyestuffs and other treating agents



3,215,486 WITH 1965 BUEI HADA ETAL LYPROPYLENE FIBERS IMPREGNATEDFIXATION OF P0 DYESTUFFS AND OTHER TREATING AGENTS Original Filed April17, 1962 l n venlor 5 By Attorney United States Patent 3,215,486FIXATION 0F POLYPROPYLENE FIBERS IMPREG- NA'IED WITH DYESTUFFS AND OTHERTREAT- ING AGENTS Buei Hada, Tsulraguchi, Amagasaki, and TomohideYasumura, Shiga-gun, Shiga-ken, Japan, assignors to Toyo Spinning (30.,Ltd., Osaka, Japan Original application Apr. 17, 1962, Ser. No. 188,195.Divided and this application July 30, 1963, Ser. No. 305,570

Claims priority, application Japan, Apr. 20, 1961, 36/14,085; Oct. 31,1961, 36/399,575 8 Claims. (Cl. 874) The present application is adivision of copending application Serial No. 188,195, filed April 17,1962.

The present invention relates to novel structured polypropylene fibresor filaments, and to treatments of such novel polypropylene fibres orfilaments.

Polypropylene fibres are notoriously poor in affinity or reactivity withdyestuffs and other treating agents, in comparison with other syntheticfibres. A number of efforts and researches have been made in this fieldto improve their reactivity or afiinity with various treating agents,particularly dyestuffs, but no fully satisfactory method has yet beendeveloped.

Therefore, it is an object of this invention to provide novel filamentsor fibres of polypropylene which are excellent in dyeability, Waterabsorbency and treating agent absorbency.

It is is a further object of this invention to provide processes fortreating such novel polypropylene fibres with dyestuffs and othertreating agents.

It is'a still further object of this invention to provide processes forpreventing the dyestuffs and other treating agents from being removedfrom the so treated fibres.

Other objects, features and advantages of this invention will beapparent from the following description and accompanying drawings inwhich;

FIG. la is an optical micrograph of a side view of a filament of thisinvention as observed by an optical microscope under dark fieldillumination;

FIG. 1b is an optical micrograph similar to FIG. 1a but showing that ofa conventional non-structured filament:

FIG. 2a is an optical micrograph of a side view of a filament of thisinvention filled with TiO as observed by an optical microscope underdark field illumination;

FIG. 2b is an optical micrograph similar to FIG. 2a but showing that ofa conventional non-structured filament;

FIG. 3a is an optical micrograph of a hand cross section (about 0.5 mm.in thickness) of filaments of this invention, as observed by an opticalmicroscope under ordinary illumination; and

FIG. 3b is an optical micrograph similar to FIG. 3a but showing that ofconventional non-structured filaments.

According to this invention there are provided structured isotacticpolypropylene filaments with numberless sub-microscopic, ultra-finevoids distributed throughout the filaments both in cross-section and inlength.

The voids contained in the novel filaments or fibres of this inventionare so small that it is difficult or rather impossible to recognize eachof these voids by means of a presently commercially available opticalmicroscope. The voids can be recognized only by an examination withelectron-microscope. However, it is very difficult to make an ultra-thinsection (less than 0.01 1) of a polypropylene fibre, and therefore onlythe existence of the voids in the sample of the structured fibres ofthis invention can be observed even with the electron-microscopicexamination and it is difficult to measure exactly the size of the voidsor their state of distribution. The size of most voids, however, isrecognized to be smaller than 0.1 with such electron-microscopicexamination.

The size, quantity, distribution, etc. of these ultra-fine voidsexisting in the new filaments of this invention can, however, bedetermined by the following means.

Each of the voids can not be recognized by means of an opticalmicropscope under ordinary or bright-field illumination. Since theresolving power of the optical microscope under bright-fieldillumination is about 0.3-0.5 the voids are substantially smaller than0.5,u in size, except of course those voids which are incidentallyformed and are also seen in usual polypropylene fibres.

When the filament of this invention is observed from the side thereof bythe optical-microscope under dark field illumination, the Whole fibreunder observation is seen to be glimmering, but it is difficult todistinguishably recognize or detect each or individual void (FIG. 1a andFIG. 2a). This may be comparable with a nebula which is glimmering as awhole but in which no individual star can be recognized. Since theresolving power of the optical microscope under dark field illuminationis less than 0.1 it can thus be said that most of the voids present inthe novel fibres of this invention are smaller than 0.1;; in size. Byway, a conventional non-structured polypropylene fibre having no suchvoids as our invention does not show glimmering phenomena, under thesimilar microscopic observation, but is seen to be transparent exceptfor those rather sharp bright spots which are caused by impurities orcracks present in the fibre (FIG. lb and FIG. 2b).

Further, the void size may also be indirectly determined from themolecular size of dyestuffs and other treating agents which cansufficiently be absorbed by the fibres of this invention. Thus, it maybe said that the fibres of this invention contain a considerable numberof voids larger than 0005 in size.

The quantity of the voids or total volume of the voids per unit weightof the novel structured filament can be determined in terms of thewater-absorbency and solventabsorbency of the fibres.

In determining the water absorbency, the polypropylene fibres are dippedin a 0.5% aqueous solution of a penetrating agent (Liponox N C K) at 20C. for 48 hours and then are dehydrated by a centrifugal dehydrator(centrifugal force 13706) for 5 minutes and weighed to measure theincrease in weight. The water absorbency is expressed by the increasedweight divided by the original weight of the fibres, in percent. The newpolypropylene fibres of this invention have more than 2.0% in waterabsorbency. In contrast thereto, the water-absorbency of conventionalpolypropylene fibres is less than 1.0%. However, there may be an errorin such Water absorbency because there occurs also an absorption of thepenetrating agent which is employed to facilitate the water penetration.For this reason, it is preferable to depend on the followingsolventabsorbency.

In determining the solvent-absorbency, the polypropylene fibres in anamount of about 0.3 g. are dipped in ml. of o-dichlorobenzene for 24hours at a room temperature (20 C.), and then are subjected tocentrifugal liquid separation by means of a centrifugal dehydrator(1370G) for 5 minutes. The fibres are weighed to measure the weightincrease, which is divided by the original weight of the fibres andexpressed in percent. The structured polypropylene fibres with voids ofthis invention have a solvent-absorbency of more than 25% and even ashigh as or more in some instances. In contrast thereto, conventionalpolypropylene fibres have a solvent-absorbency of less than 20%.

The voids are distributed throughout the polypropylene fibre orfilament, both in the longitudinal and transverse directions of thefibre. This distribution is evident from the fact that, as mentionedbefore, the fibre of this invention is glimmering in its entirety whenobserved by an optical microscope under dark-field illumination. Each orindividual void is very difficult or rather impossible to be identified.This is apparent, for example, from the micrograph of FIG. 1a. Incontrast thereto, in a conventional polypropylene fibre, no suchglimmering appears under the same microscopic observation, but there areobserved sharp or distinctive strong bright spots which are caused bynon-transmittent impurities or cracks present in the fibre and which aredifferent and distinguishable from the glimmering of our fibres.

A unique feature of the fibres of this invention by virtue also of whichthey are sharply distinguishable from known polypropylene fibres is inthe fact that when handout sections (each about 0.5 mm. in thickness) ofthe fibres of this invention are observed through an optical microscopeunder bright-field or ordinary illumination, they appear cloudy andlight yellow or dark yellow throughout the sectional area, but no suchphenomena is seen in conventional polypropylene fibres having no suchvoids as this invention. This fact will be apparent from the comparisonof FIG. 3a and FIG. 312, color being omitted.

The novel polypropylene fibres or filaments of this invention can thusbe well defined by the various factors mentioned hereinabove.

The novel polypropylene fibres can not be produced by methodsconventionally employed for manufacturing porous, spongy or foamedarticles of synthetic resins. Thus, the novel fibres can not be producedby employing a blowing or gasifiable agent such as volatile solvent e.g.xylene or by treating fibres with a swelling agent (e.g., chlorobenzene,tetraline) for polypropylene.

One method for producing the novel fibres is to homogeneously mix awater soluble salt in solid state of a size smaller than about 0.5 indiameter with a molten polypropylene resin, which is extruded through aspinning nozzle to form filaments. The filaments, after being cooled andstretched, are immersed in warm water for a long time to dissolve theultra-fine salt particles out of the fibres. However, this procedure isdiflicult to operate and the produced fibres are poor in mechanicalstrength.

We have discovered that the polypropylene filaments having the novelstructure described before can conveniently be produced by the followingmethod.

Preferably, a fibre-forming homopolymer of propylene is used, but afibre-forming resin consisting of a copolymer of propylene with a smallamount (less than 15%) of an olefinic monomer such as ethylene, buteneor a diene monomer such as butadiene, isoprene may be employed. Ifdesired, a fibre-forming resin blend composed of a predominant amount ofa propylene polymer and a small amount (less than 15 of at least onepolymer of the above mentioned olefinic or diene compound may also beused. Therefore the term polypropylene as used throughout thespecification and claims is intended to include propylene homopolymers,polymer blends and copolymers mentioned above. As for the fibre-formingresin, it is preferable to employ an isotactic polypropylene resinhaving a relatively small molecular weight (preferably about 30,000 to80,000) and a large melt index (as measured by the method ofASTM-D-1238-57 TE).

The above resin is heat melted and extruded through a spinning nozzle ata temperature as low as possible within a temperature range whichpermits satisfactory spinning of the molten resin. If desired a fillersuch as titanium oxide, anti-oxidant, stabilizer, etc. which areconventionally used as additives for polypropylene may be added to themolten resin in a conventional manner and amount as well known in theart. Generally the resin is extruded at a temperature of from 200 C. to260 C. through a conventional spinning nozzle and the filaments arecooled and solidified. In this case it is important that the cooling beeffected slowly to obtain unstretched filaments having the so-calledmonoclinic crystalline structure and a high degree of crystallization.Thus, for example, there is provided a first cooling zone extending atleast about 5 cm., preferably 10-20 cm., downwardly from the lower faceof the nozzle. The first cooling zone is constituted by ambientatmosphere heated to a temperature between 100 C. and 160 C. by asuitable means such as heating by infrared ray, electric heater, steamor the like. Below the first cooling zone and extending downwardlytherefrom is a temperature controlling cylinder or chamber providing asecond cooling zone therein. Into and through this chamber is passed acurrent of an inert gas such as nitrogen gas or air preheated at atemperature between C. and C. The temperature control of the chamberdescribed above may be effected, if necessary, by providing a suitableheating or cooling means with the chamber or cylinder. The length of thechamber may vary depending upon the spinning condition, but usually alength of about 1-4 m. is employed. Any other suitable means may beemployed to effect a slow cooling which would result in the productionof unstretched fibres having monoclinic structure.

During passage through the controlled cooling zone the filaments aregradually and slowly cooled to obtain unstretched filaments withmonoclinic crystalline structure. The non-stretched fibres shouldpreferably be high in the degree of crystallinity and also in molecularorientation.

As the crystallization proceeds the specific gravity of the fibres orfilaments increases, and therefore the degree of crystallinty of fibrescan be determined in terms of the specific gravity of the fibres.Meanwhile, as the molecular orientation increases, the index ofbirefringence increases, while the degree of orientation as determinedby the half width of diffraction curve of X-ray pattern is alsoincreased. Therefore, the degree of molecular orientation can bedetermined by measuring these values.

The specific gravity of fibres is measured by means of a "densitygradient tube of an isopropanol-water system at 30 C. after 24 hours. Ifthe fibres contain a filler such as titanium oxide it must becompensated in determining the specific gravity. It is necessary thatthe non-stretched fibres have a specific gravity higher than 0.890 asmeasured above.

The degree of orientation may be determined in terms of the index ofbirefringence of the fibres. The index of birefringence is calculated bythe following formula:

Index of birefringence= wherein d is the diameter of a single fibre, nis the refraction index .parallel to the fibre axis, n is the refractionindex vertical with respect to the fibre axis, an 1 is the value ofretardation as measured by a polarizing microscope with a Berekcompensator. It is necessary that the non-stretched fibres have an indexof birefringence higher than 0.010, preferably higher than 0.012.

Alternatively or additionally, the degree of molecular orientation offibres may also be determined as follows:

The fibres are superposed in alignment to a thickness of 50 mg./cm. ThenX-ray is irradiated to the fibres in the direction perpendicular to theaxial direction of the fibres and the (110) diffraction intensity ismeasured along the Debye-ring to plot a curve. From this curve ismeasured to half width ([3), while compensating for the scatteringcaused by the non-crystalline portion. The degree of orientation iscalculated from the following formula:

Degree of orientation (percent) Bow-5 X 100 The non-stretched fibrescoming out of the cooling zone are then wound or collected on a drum orbobbin. Since the non-stretched filaments or fibres should have a highdegree of orientation as mentioned above, it is preferable that thefibres are wound at a high speed (e.g. higher than 200 m./min.) and thedrawing ratio (ratio of the filament vw'nding speed to the speed offilaments at the spinning nozzle) is high, namely higher than 200 andmore preferably higher than 300. In any event it is important that thefibres are so spun and drawn that their degree of orientation is withinthe range specified above.

As mentioned above, the non-stretched fibres should have a specificgravity higher than 0.890, most of the fibres so produced have aspecific gravity lower than 0.900. Therefore, it is preferable tosubject the fibres to a seasoning or aging treatment to promotecrystallization so that the specific gravity is increased up to 0.900 orhigher. If the fibres spun and drawn as mentioned above have a specificgravity higher than 0.900 it is not always necessary to carry out theseasoning treatment although it is preferable to carry out suchtreatment in any case.

The fibres may be subjected to the seasoning treatment, in any form suchas in the form of tow, as wound on a bobbin or reel. The seasoning maybe effected under atmosphezic conditions, but preferably in hot air orsteam.

The temperature of the aging may vary widely within the range from C. to160 (3., preferably from 60 C. to 140 C. The time of aging may also varyfrom a few seconds to several tens of hours, and may be shorter at ahigher temperature within the range specified above. Preferably, thetreatment or aging is conducted at a temperature of from 100 C. to 130C. for minutes to 1 hour. In any event, however, it is necessary thatthe aging is effected so that the resulting fibres have a specificgravity of higher than 0.900, preferably higher than 0.903 when measuredby the method specified before.

As mentioned above, it is preferable to collect or wind the unstretchedcold fibres on a bobbin, drum or the like before subjecting to theseasoning or aging treatment. However, if desired, the formed filamentsmay be subjected directly to the seasoning or aging treatment withoutcollecting or winding on a bobbin or drum as mentioned above.

The seasoned or aged fibres are then subjected to stretching. Thestretching may be effected in a conventional manner. Thus the stretchingis conducted by passing the fibres through a hot medium conventionallyemployed in the art of stretching, such as hot air, hot water 'orpressured steam at a temperature between 90 C. and 140 C. During thepassage through the hot medium the fibres are stretched. A higherstretching ratio is preferred, and usually the fibres are stretched from1.5 to 7 times their original length. The temperature for carrying outthe stretching is preferable to be lower within the range specifiedabove.

During this stretching stage, voids of the present invention are formedin the fibres.

The structured polypropylene fibres thus obtained have ultra-fine voidsdistributed throughout the same as detailed before and yet havemechanical properties comparable with those of conventionalpolypropylene fibres. Thus, for example, the fibres with such voids ofthis invention can have a strength of 3-9 g./denier and an elongation of20-100%.

Since the fibres or filaments of this invention contain numberlessultra-fine voids, they can satisfactorily absorb various dyestuifs suchas azoic or naphthol dyes, dispersed dyes, oil dyes, metallized dyes,vat dyes, sulfur dyes, acid dyes, basic dyes, mordantable dyes so thatthey are readily dyed deeply and uniformly. Furthermore, the fibres canuniformly and sutficiently absorb other treating agents such aspolymerizable compounds (e.g. vinyl monomers), heat-stabilizers,light-stabilizers, antistatic agents, etc.

The important and remarkable advantages of the fibres of this inventionreside in the fact that the fibres can be readily treated with the abovementioned dyes and other treating agents with excellent aifinity. Inview of the fact that polypropylene fibre-s are notorious for fatallypoor afiinity or reactivity with dyestuffs and other treating agents, itis surprising that the treated fibres of this invention are excellent infastness. It is believed that this excellent fastness in our novelpolypropylene fibres is due to the extremely small size of the voidswhich are distributed throughtout the fibres as explained before. Thus,when the fibres of this invention are treated with a treating agent, thelatter will readily penetrate impregnatingly into the fibres. Once thetreating agent has penetrated into the voids, it is retained therein bythe ad-sorptive power of the polypropylene and is brought into suchstate that it will not leave the fibres. Although the adsoiptive powerof polypropylene itself is rather poor, the voids are so small in sizethat the adsorptive power in each void is sufiiciently high to firmlyretain the molec-ule (s) of the treating agent therein. This explanationis evidenced by the fact that the solvent retentivity of the fibres ofthis invention is higher than 1% (and even as high as 40% or more insome instances). This feature is unique in the fibres of this inventionand can not be seen in polypropylene fibres of the prior art. Thesolvent retentivity is measured as described in Example 1 hereinaftergiven.

Further distinctive feature of the fibres of this invention is in thefact that they have a water-retentiviy higher than 1%, and even higherthan 10% in some cases. As well known, polypropylene fibres are mosthydrophobic among known synthetic fibers and their water-retentivity isusually below 0.1%. Therefore conventional polypropylene fibres areextremely high in electrostaticity which causes various troubles inhandling such as spinning, weaving, finishing, etc. In contrast thereto,the polypropylene fibres of this invention can retain a larger amount ofwater as mentioned above and therefore the electrostaticity is decreasedso that the fibres of this invention do not exhibit the disadvantagescaused by electrostaticity. The Water-retenticity as mentioned herein ismeasured by the method described in Example 1 hereinafter given.

As explained before, the fibres of this invention have ultra-fine voidstherein and according are excellent particularly in dyeability. Examplesof dyestuffs and intermediates thereof useful in dyeing thepolypropylene fibres of this invention are oil colors such as SolventYellow 2 (C.I. 11020), Solvent Yellow 5 (C.I. 11380), Solvent Yellow 14(C.I. 12055), Solvent Orange 7 (C.I. 12140), Solvent Red 4 (C.I. 12170),Solvent Red 24 (C.I. 26105), Solvent Brown 5 (C.I. 12020), etc.;dispersed colors such as Disperse Yellow 1 (C.I. 11855), Disperse Yellow3 (C.I. 11855), Disperse Yellow 7 (C.I. 26090), Disperse Yellow 31 (C.I.4800), Disperse Yellow 33, Disperse Orange 5 (C.I. 11100), Disperse Red1 (C.I. 11110), Disperse Red 7 (C.I. 11150), Disperse Red 9 (C.I.60505), Disperse Violet 6 (C.I. 61140), Disperse Violet 12 (C.I. 11120),Disperse Blue 23 (C.I. 61545), Disperse Black 1 (C.I. 11365), DisperseBlack 3 (C.I. 11025), etc.; sulfur colors such as Sulfur Yellow 4 (C.I.53160), Sulfur Blue 2 (C.I. 53480), Sulfur Blue 5 (C.I. 53235), SulfurGreen 6 (C.I. 53530), etc.; vat colors such as Vat Yellow 20 (C.I.68420), Vat Orange 5 (C.I. 73335), Vat Red 1 (C.I. 73360), Vat Blue 3(C.I. 73055), etc.; diazo components of azoic colors such as aniline,chloroaniline, 2-amino-5-nitroanisole, nitroaniline, toluidine,phenetidine, 4-benzamide-2,5- dimethoxyaniline, 4-amino-4'methoxydiphenylamine, 4,4-diamino-di-phenylamine, etc.; couplingcomponents for azoic colors such as B-naphthol, a-naphthylamine, 3-hydroxy-2-naphthoanilide, 3-hydroxy-N-1-naphthyl 2- naphthoarnide,4,4-bisacetoamide, 4,4 bisacetoaceto-otoluidine,3-hydroxy-N-2-naphthyl-2-naphthoarnide,3-hydroxy-2-naphtho-4-chloro-o-toluidine, 2 a-acetylacetoamide 6ethoxybenzothiazole, 3-hydroxy2',5'-dimethoxy-2-naphthoanilide,a,u-terephthaloy1-bis(4-chloro methyl-o-acetoanisidide), etc.; basiccolors such as Basic Yellow 2 (CI. 41000), Basic Orange 2 (CI. 11270),Basic Red 1 (Cl. 45160), Basic Violet 3 (C.I. 42555), Basic Blue 24 (CI.52030), Basic Brown 1 (CI. 21000), etc.; triazines containing one or twohydrogen atoms on the triazine ring, and dyestuffs containing such atriazine;

halogenated alkylene acylhalides, and dyestuffs containing such a.acylhalide; reactive colors such as dyestuffs containing an epoxyradical; various Whitening agents such as those of the stilbene type,imidazole type, thiazole type, oxazole type, imidazolone type, triazoletype, oxazole type, imidazolone type, cumarine type, carbostyn'l type,biphenyl type, pyridine type, pyrazoline type, etc. various pigmentssuch as Pigment Yellow 1 (Cl. 11680), Pigment Orange 5 (CI. 12075),Pigment Red 3 (Cl. 12120), Pigment Blue 1 (Cl. 42595), carbon black,etc.; acid dyes such as Acid Yellow 72, Acid Red 139, Acid Blue 138(C.I. 62075), Acid Blue 139, Acid Brown 49, Acid Green 27, Acid Violet51, etc.; metal-containing dyes such as Acid Yellow 116, Acid Orange 88,Acid Red 211, Acid Blue 168, Acid Brown 19, Acid Violet 68, Acid Yellow101, Acid Orange 62, Acid Red 183, Acid Blue 158A, Acid Green 12, AcidViolet 56, etc.

Various other treating agents such as light-stabilizers,heat-stabilizers, surfactants, softeners, flame resistors, antistaticagents, mordanting agents, etc. are also satisfactorily absorbed by thenovel fibres of this invention. Ex amples of light-stabilizers aresalicylic acid esters or their derivatives, benzophenone derivativessuch as 2-hydroxy- 4-dodecyloxybenzophenone, p-phenylenediamine andderivatives thereof, benzotriazole derivatives; organic sulfurcompounds, etc. Examples of heat-stabilizers include various phenolderivatives which are known in the art.

Among the dyestuffs and treating agents mentioned above, those organiccompounds having a molecular weight not more than 500 and containing nosuch extremely hydrophilic groups as sulfonic acid group, carboxylicacid group, sulfuric acid group, ammonium group, etc. are preferred.

In applying these dyestuffs and other treating agents to the novelstructured polypropylene fibres of this invention, the dyestuffs ortreating agents may be employed in the form of aqueous solution, aqueousdispersion or nonaqueous dispersion. It is also possible to employ themin the form as dissolved or dispersed in a mixture of water andnon-aqueous medium. Example of such non-aqueous mediums are loweraliphatic alcohols such as methanol, ethanol, etc.; lower aliphaticketones such as acetone, methyl ethyl-ketone, cyclohexanone; loweraliphatic acid esters such as ethyl formate, butyl acetate, etc.;halogenated hydrocarbons such as carbon tetrachloride, tri chlene,perchlene, chlorobenzene, etc.; hydrocarbons such as heptane,cyclohexane, benzene, xylene, tetraline, decaline, etc.;nitrogen-containing organic compounds such as pyridine, formamide,dimethylformamide, etc.; ethers such as methyl ether, ethyl ether,dioxane, etc. A mixture of two or more of these organic solvents mayalso be used.

Although a solution or dispersion of a dyestuff or treating agent in anon-aqueous medium alone may be used, it is preferable to use an aqueousliquid mixed with 0.530% by weight of a non-aqueous solvent as themedium for the dyestuff or treating agent in order to avoid hardening ofthe polypropylene fibres as far as possible.

In preparing a dispersion of a dyestuff or other treating agent, adispersing agent may be used. in a conventional manner to facilitatedispersion and stabilize the same. Any of anionic, cationic, non-ionicand ampheionic surfactants which are well known in the art may be usedas the dispersing agent. The amount or concentration of the dispersingagent may vary depending upon the particular dyestutf, treating agentemployed, amount thereof, the particular non-aqueous medium and itsamount, etc. Generally, the dispersing agent is employed in aconcentration of about 0.01% to 3% by weight in the medium.

In treating polypropylene fibres of this invention with a treatingliquid (a dispersion or solution of a dye or a treating agent asmentioned above), the fibres are immersed in the treating liquid at araised temperature, preferably higher than C., for a sufficient time sothat the fibres are fully impregnated with the treating liquid.Alternatively the treatment may be carried out by the socalled paddingmethod wherein the fibres are dipped in a concentrated treating liquidfor a short time, squeezed uniformly and treated at a high temperature(e.g. higher than C.).

When the fibres are so treated, the dyestulr' or treating agentpenetrates into the fibres and is retained fastly therein so that itwill not readily be removed from the fibres during the usual handling ofthe fibres such as wearing and laundering. However, the fastness,particularly washing fasteness, is further remarkably improved if the sotreated fibres are subjected to an after-treatment for enlarging themolecular dimensions of the dye or treating agent as absorbed in thefibres and/ or reducing, diminishing or even substantially dissipatingthe voids, as detailed below.

In order to carry out an after-treatment for enlarging or increasing themolecular dimensions of the compound absorbed in the fibres, the fibresmay be treated with a compound which is capable of reacting with thecompound contained in the fibres to enlarge or increase the moleculardimensions of the latter. However, it is preferable to preliminarilyimpregnate the fibres with compounds which are capable of reacting witheach other to produce a compound of larger molecular dimensions and thensubjecting the fibres to conditions under which the said reaction takesplace. Thus, for example, an aromatic compound (diazo component) havingan active amine group and a coupling component such as naphthol,naphthylamine, active methylene compound are absorbed together in thefibres in a manner as described before, and then the fibres are treatedat a temperature of 60-100" C. for 1060 minutes in the presence of anacid and nitrite so as to diazotize the diazo component and couple thesame with the coupling component. The polypropylene fibres dyed in thismanner are class 5 in fastness to washing (AATCC-NO. 2), class 5 infastness to rubbing (as measured by the friction tester, Japan Societyfor Promotion of Scientific Research) and class 4-5 in fastness to light(as measured by Fade-O-Meter for 20 hours) and the dyed fibres were deepand fast. Another example is to absorb a compound having an active aminogroup and a triazine having at least one halogen atom together in thefibres and then to treat the fibres at a temperature of 40100 C. in thepresence of an alkaline substance such as caustic soda, sodium carbonateor the like so asto react the compounds forming a molecularly largerdyestuff within the voids of the fibres. A further example is to absorban aromatic amine and a quinoline (or a phenol) together in the fibresand subsequently react them with each other. A still further example isto absorb thioindoxyl carboxylate and an aromatic nitroso compound inthe fibres and then to react them with each other. In any event,compounds of larger molecular dimensions are produced within the voidsin the fibres and their fastness or washability is remarkably improved.It is also possible to absorb an alkylene oxide in the fibres and thento ring-opening-polymerize the alkylene oxide. Still another example isto absorb an epoxy radical-containing compound and an active aminocompound together in the fibres and then to react them within the voidsin the fibres. Other methods will be apparent to those skilled in theart from the above examples.

In addition or alternatively to the above treatment for enlarging orincreasing the molecular dimensions of the compounds absorbed in thefibres, it is preferable to reduce, diminish or substantially dissipatethe voids to em- 9 bed or confine the dyestuff or treating agent Withinthe fibres.

In reducing, diminishing, vanishing or dissipating the voids of thefibres after treated with dyestuffs or treating agents as explainedbefore, the treated fibres are brought into contact with a vapor of anorganic compound or solvent which is capable of swelling or plasticizingpolypropylene resin, or the fibres are impregnated with the said solventand then the solvent is gradually evaporated. Alternatively, the treatedpolypropylene fibres, in relaxed state, are exposed to an atmosphere ata temperature of 120160 C. and substantially free from the solventmentioned above. These treatments are effective not only in improvingfastness of the treated fibres as mentioned above but also in improvingthe transparency.

Examples of the organic compounds or solvents which are capable ofswelling or plasticizing polypropylene resins and which are useful inthe above mentioned void diminishing, reducing or dissipating treatmentare aliphatic hydrocarbons such as hexane, heptane, octane, etc., cyclichydrocarbons such as benzene, toluene, xylene, tetraline, decaline,etc.; halogenated hydrocarbons such as carbon tetrachloride,tetrachloroethane, chlorobenzene, etc.; ketones such as methyl ethylketone, cyclopentanone, cyclohexanone, etc.; esters such as ethylformate, butyl acetate, etc.; alcohols such as ethyleneglycol,cyclohexanol, etc. which have an afiinity with polypropylene.

In carrying out the solvent treatment, the solvent is vaporized byheating or under vacuum and the fibres are placed or hung in the vaporatmosphere so that they are contacted with the vapor. Alternatively,pines, bars, rollers, drums or the like are arranged to define a zigzagpassage for the fibres. During passing through the zigzag passage thefibres are exposed to a stream of the solvent vapor.

An alternative solvent treatment is carried out by impregnating thefibres with the solvent and subsequently evaporating the solvent slowlyat a temperature preferably below 100 C.

In carrying out these solvent treatments care should be taken not toexcessively swell or plasticize the fibres. An excessive swelling orplasticizing will cause the tendency of the fibres after drying towardhardening, flattening in cross-sectional shape and adhering with eachother. If there is a danger of such excessive swelling or plasticizingit should be controlled by a suitable means such as by decreasing theafiinity of the solvent with polypropylene by adding thereto a suitableamount of other solvent (such as a lower aliphatic alcohol, e.g.methanol, ethanol, etc.) which is comparatively weak in afiinity withpolypropylene. The action of the solvent may also be controlled bydecreasing the temperature and/or by controlling the time of treatment.

It will be understood that the conditions of the solvent treatment maybe experimentally selected depending upon the particular solventemployed, particular nature of voids present in the fibres to betreated, etc.

The other method for reducing, diminishing or substantially dissipatingthe voids of the fibres is to expose the fibres to an atmosphere at atemperature between about 120 C. and 160 C. substantially free from suchsolvent as mentioned before. This method may be carried out, forexample, by treating the fibres by hot air in a conventional heattreating machine or by contacting the fibres with a surface heated at atemperature mentioned above. The time of this heat treatment may varydepending upon the temperature, but usually within the range from 1 to30 minutes.

While the treatments with dyes and other treating agents, and forenlarging the molecular dimensions of the treating agents and forreducing, diminishing or dissipating the voids have been explained asapplied to fibres or filaments, the same treatments may equally beapplicable to various types of products (e.g. yarns, threads, fabrics,

, 10 articles of clothing, etc.) made of the fibres. Therefore, the termfibres, filaments or the like as used in connection with thesetreatments is intended to mean also the products thereof.

Throughout the specification including the following examples, theoptical microscopic observation was made by using SKO-Type opticalmicroscope (manufactured and sold by K. K. Shimadzu Seisakusho, Kyoto,Japan) with an ocular or eye-piece of Heugens (X10) and an objective ofAchromat (X40, number of aperture 0.65). The resolving power of thismicroscope under ordinary illumination was about 0.5a. In theobservation under dark-field illumination the above microscope wasattached with a conventional condenser for dark-field illumination. Theresolving power of the microscope under the dark-field illumination wasabout 0.1,u. The microscopic observation was carried out in the usualmanner.

Example 1 An isotactic polypropylene resin of 63,000 in molecularweight, 4.80 in melt index and 0.6% in the n-heptane extract was meltedat a temperature of 240 C. The molten polypropylene was fed by aconventional measuring gear pump to a spinning nozzle with holes (each0.8 mm. in diameter) to be extruded therethrough at a tem erature of 235C. Below the spinning nozzle there was provided an enclosure extending(5 cm. in length) downwardly from the lower face of the nozzle. Theenclosure was surrounded by an electric heating element to heat theinterior of the chamber at a temperature of C. Below the said enclosurewas connected a temperature controlling cylinder (3.5 m. in length)depending downwardly therefrom. Preheated air was introduced into thiscylinder to maintain the interior temperature of the cylinder at 80 C.The extruded filaments were passed, downwardly through the firstenclosure and the temperature controlling cylinder to be gradually andslowly cooled, and then Wound on a bobbin arranged below the temperaturecontrolling cylinder at a speed of 650 rn./min. (drawing ratio 520). Thenon-stretched fibres wound on the bobbin were left standing for one hourwithin a thermostatic chamber of 105 C. and then stretched 3.4 timestheir original length in hot water at 100 C. Thereafter the stretchedfibres were heat treated at C. for 30 minutes under tension.

The specific gravity of the non-stretched fibres before the seasoningtreatment Was 0.894, and their index of birefringence was 0.0121. Afterthe seasoning treatment but before stretching, the fibres had a specificgravity of 0.904. The structured-polypropylene fibres after the final orstretching treatment had a water-absorbency of 17.6%, asolvent-absorbency of 57.6%, a water-retentivity of 4.1% and asolvent-retentivity of 6.5%.

The water-retentivity of the fibres has been determined by the methodwherein a centrifugally dehydrated sample as prepared in thedetermination of water-absorbency mentioned before was left standing for24 hours in an atmosphere of 60% in relative humidity at 20 C. andweighed to measure the weight increase as compared with the originalweight of the fibres. The water-retentivity is expressed by theincreased weight divided by the original weight by the fibres, inpercent. The solvent-re tentivity was measured in the same manner as thewaterretentivity except that a centrifuged sample as prepared in thedetermination of solvent-absorbency mentioned before was employed.

When the structured polypropylene fibre was observed from the sidethereof by the optical microscope under dark-field illumination, thewhole was seen to be glimmering and it was impossible to distinguishablyrecognize each or individual void. When hand cut sections (each 0.5 mm.in thickness) of the structured polypropylene fibres were observedthrough the optical microscope under ordinary illumination they appearedcloudy yellow uniformly throughout the whole sectional area. Thestrength 1 i of the fibres was 4.5 g./denier, and the elongation was60%.

The structured polypropylene fibres were dyed in a 1.5% OWF aqueousdispersing liquid of refined Celiton Fast Red 46 (bath ratio 1: 100) at100 C. for one hour and rinsed with water. The amount of the dyeabsorbed by the fibres was 9.04 mg. per gram of the fibres, which weredyed deeply and fastly.

Example 2 The procedure of Example 1 for the production of structuredpolypropylene fibres was repeated except that the spinning temperatureat the nozzle was 250 C. The structured polypropylene fibres thusproduced had a water-absorbency of 6.2%, water-retentivity of 1.2%,solvent-absorbency of 6.2%, solvent-retentivity of 2.8%, and index ofbirefringence of 0.011. The optical-microscopic observations of thefibres showed similar results as those of Example 1. The amount of thedye absorbed by the fibres was 3.40 mg. per gram of the fibres, whichwere dyed deeply and fastly. The specific gravity of the fibres beforethe seasoning or aging treatment was 0.892.

Example 3 A blend of 95% of the polypropylene resin employed in Example1 and 5% of an epoxy resin (Epikot 1009) was spun and treated as inExample 1 except that the spinning temperature at the nozzle was 250 C.The Water-absorbency, solvent-absorbency, water-retentivity,solvent-retentivity and results of the microscopic observations of thefibres thus obtained were substantially identical with those ofExample 1. When dyed as in Example 1 the amount of the dyestuff absorbedwas 11.3 mg. per gram of the fibres, which were more deeply and fastlydyed.

Example 4 Structured polypropylene fibres having voids produced by thesame manner as Example 1 were dipped in an aqueous liquid in which weredispersed 3-hydroxy-2-naphthoo-toluidine and 4-amino-3-nitrotoluene,each based on the weight of the fibres, by the aid of a nonionicdispersing agent. The temperature of the bath was increased from 60 C.up to 120 C. which temperature was maintained for one hour. Then thefibres were dipped in an aqueous solution containing 12% (based on thefibre weight) of sulfuric acid and 8% (based on the fibre weight), forminutes at 70 C. to effect the diazotizing reaction. In this way thefibres were dyed to deep red. The fastness of the dyed fibres wasexcellent and was class 4 in fastness to light and class 5 in each offastness to Washing and fastness to rubbing.

Example 5 The procedure of Example 1 for the production of structuredpolypropylene fibres with voids was repeated except that the temperaturewithin the temperature con trolling cylinder was maintained to be about75 C. and that the seasoning treatment was carried out at 120 C. for onehour and the stretching was 4.0 times the original length. Before theseasoning treatment the fibres had a specific gravity of 0.895 and anindex of birefringence of 0.015. After the seasoning but before thestretching, the fibres had a specific gravity of 0.903. After the finalor stretching treatment, the structured polypropylene fibres was 31.7%in water-absorbency, 8.7% in water-retentivity (measured as in Example1), 70.5% in solvent-absorbency and 7.2% in solvent retentivity(measured as in Example 1). When dyed as in Example 1, the dyestufi" wasabsorbed by the fibres in an amount of 12.4 mg. per gram of the fibres,which were dyed deeply. The results of the microscopic observations ofthe fibres before dyeing were same as those of Example 1 and the fibreshad a strength of 6.2 g./denier and elongation of 1 2 Example 6 Thestructured polypropylene fibres prepared by the procedure of Example 3,but before dyeing, were dipped in an aqueous bath (bath ratio 1:40)wherein were dispersed 8% OWF of Disperse Blue 1 (C.I. 64500) and 5% OWFof 2,4-dichloro-6-aniline-1,3,5-triazone with the aid of an anionicsurfactant. The temperature of the bath was increased to 120 C. whichtemperature was maintained for one hour. The dyed fibres were washedwith water and dipped in an aqueous solution containing 1% of sodiumcarbonate and treated therein for 30 minutes at C. Then the fibres werewashed with water and dried. The fibres could be dyed deeply and fastly.

Example 7 The structured polypropylene fibres prepared by the procedureof Example 1, but before dyeing were dipped in 100% ethyleneimine andtreated for one hour at 30 C. After squeezing, the fibres were dipped ina. slightly acidic water at 5 C. for 30 minutes. Then the fibres werewashed with water, dehydrated and dried. The treated polypropylenefibres were excellent in antistaticity and dyeability.

Example 8 An isotactic polypropylene resin (same as that employed inExample 1) was spun by the same spinning apparatus as Example 1 exceptthat the spinning temperature at the nozzle was 250 C. and the windingspeed was 650 m./min. (drawing ratio 520). The non-stretched fibres thusproduced were 0.8915 in specific gravity, 0.011 in index ofbirefringence, and had a monoclinic crystalline structure. A sample(wound on bobbin) of the nonstretched fibres was subjected to seasoningat C. for one hour. The other sample (wound on bobbin) of the samenon-stretched fibres was subjected to seasoning at 130 C. for one hour.In both cases, the fibres after the seasoning treatment had a monocliniccrystalline structure. The fibres seasoned at 105 C. had a specificgravity of 0.9032 and an index of birefringence of 0.016, while thefibres seasoned at 130 C. had a specific gravity of 0.9088 and an indexof birefringence of 0.017. These fibres were stretched 3.5 times theiroriginal length in hot water of 100 C. and then set under non-tension indried air at C. for 30 minutes. The results of opticalrnicroscopicobservations on these final fibres were similar to those of Example 1.The final fibres produced through seasoning at 105 C. absorbed 6.48 mg.of the dye per gram of the fibres when dyed as in Example 1 and had awater-absorbency of 10.5%, while the fibres produced through seasoningat C. absorbed 10.32 mg. of the dye per gram of the fibres and had awater-absorbency of 27.4%.

Example 9 The structured polypropylene fibres produced by the procedureof Example 8 wherein the seasoning treatment was effected at 130 C. weredipped in a bath (bath ratio 1:10) of warm water containing 0.01% of anonionic surfactant. Then Disperse Orange 1 (C.I. 11080) and 48% aceticacid were added to the bath so that the bath will be 2% in the dyeconcentration and 1% in the acid concentration. The fibres were dyed inthis bath at 100 C. for 60 minutes. After dyeing, the fibres were rinsedwith water, squeezed uniformly and air dried. The dyed fibres were thenplaced in a chamber containing n-heptane. The chamber was closed and theinterior was made vacuum maintained at 60 C. After one hour the fibreswere transferred from the chamber to a dryer at 70 C. to slowly dry thefibres. The fibres were dyed deeply and excellent in fastness.

Example 10 The fibres produced by the procedure of Example 3, but beforedyeing, were treated by passing zigzag through and along rollersarranged within a closed chamber. During the passage through the chamberthe fibres were exposed to a vapor stream (at 85 C.) of a mixture ofcarbon tetrachloride and ethanol (1:1). By this treatment the fibreswere improved in luster and their dyeability (absorptivity of dyestuffs)was decreased. The microscopic observations of the fibres disclosed thatthe voids had substantially dissipated.

Example 11 An isotactic polypropylene resin (same as that used inExample 1) was spun by the same spinning apparatus as in Example 1,except that the spinning temperature at the nozzle was 235 C. and thewinding speed was 350 m./min. (drawing ratio 280) in one experiment and800 m./min. (drawing ratio 640) in another experiment. In both cases thenon-stretched filaments obtained were monoclinic in crystallinestructure. The unstretched fibers wound at the speed of 350 m./min. hada specific gravity of 0.8956, an index of birefringence of 0.007 and adegree of orientation of 73%, while the fibres wound at the speed of 800m./ min. had a specific gravity of 0.8938, an index of birefringence of0.016 and a degree of orientation of 92%. These samples were subjectedto seasoning at 105 C. for one hour and stretched 3.5 times theiroriginal length in hot water. After this treatment voids were producedin the fibres which were wound at 800 m./min., but not in the fibreswhich were wound at the speed of 350 m./min.

Example 12 The filaments of Example 11 wherein the winding speed was 800m./min. could 'be dyed as in Example 4 to deep shades and fastly as inExample 4.

Example 13 The unstretched fibres obtained in Example 2 were heattreated at 100 0., 120 C. and .140 C. respectively, for 30 minuteswithout tensioning. The dye absorbency (Celliton Fast Red 4G),water-absorbency and water-retentivity of these fibres were as follows:

Microscopic observations of the fibres heat-treated at 100 C. and 120 C.respectively disclosed the formation of voids, but not for the fibrestreated at 140 C.

Example 14 The fibres of Example 13 wherein the heat-treatment waseffected at 120 C. were heat treated at 145 C. for minutes, so that thevoids were almost disappeared.

Example 1 5 A polypropylene resin of 143,000 in molecular weight and1.28 in melt index (by ASTMD-123857 TE method except that the load was 5kg.) was spun by the same apparatus as Example 1 except that thespinning temperature at the nozzle was 280 C. and the winding speed was675 m./min. (drawing ratio 540). The non-stretched fibres thus producedhad a specific gravity of 0.8863 and an index of birefringence of 0.009,and was smectic in crystalline structure. The non-stretched filamentswound on a bobbin were subjected to a seasoning treatment at 105 C. forone hour. After seasoning the filaments were stretched 80% of maximumpossible stretch at which the fibre breaks. However no void formationoccurred in the fibres.

When the same procedure was repeated except that the spinningtemperature was raised to 270 C., fibres having voids of this inventionand excellent in dyea-bility were obtained. In this case, thenon-stretched fibres had a specific gravity of 0.8973 and an index ofbirefringence of 0.018, and were monoclinic in the crystallinestructure.

1 4 Example 1 6 A polypropylene polymer (same as that used in Example 1)was extruded at 250 C. through a spinning nozzle having 24 holes (each0.8 mm. in diameter). No first enclosure as in example was providedbelow the nozzle, but only a temperature controlling cylinder wasconnected adjacent and below the nozzle. Air preheated at C. wasintroduced into the temperature controlling cylinder. The spun filamentsafter passing through this cylinder were wound at a speed of 600 m./min.(drawing ratio 430). The non-stretched filaments thus produced had aspecific gravity of 0.8968 and an index of birefringence of 0.014. Thefilaments as wound on a bobbin were subjected to a seasoning treatmentat C. for one hour, and then stretched 3.5 times their original lengthwithin a dry heat stretching cylinder interior of which was maintainedat C. Then the filaments were wound upon a bobbin and heat treated at C.for '15 minutes. Void formation occurred in the filaments so treated.The structured filaments could be deeply dyed with Celliton Fast Red 4G.The fibres had a breaking strength of 4.5 g./d. and an elongation of40%.

What We claim is:

1. A melt-spun structured polypropylene fiber having numberlessultra-fine voids distributed throughout the fiber and having an initialsolvent-absorbency greater than 25%, said voids being so fine and sodistributed throughout the fiber that it is difiicult to distinguishablyrecognize the individual voids under observation by an opticalmicroscope in bright field illumination, the whole fiber having aglimmering aspect when observed by an optical microscope under darkfield illumination. said fiber containing in the voids at least onesub-stance selected from the group consisting of dyestuffs, theirintermediates, light-stabilizers, heat-stabilizers, surfactants,softeners, flame resistors, antistatic agents, mordanting agents,polymerizable compounds, solvents and water.

2. A method for preparing a melt-spun structured polypropylene fiberhaving numberless ultra-fine voids distributed throughout the fiber andhaving an initial solvent absorbency greater than 25%, said voids beingso fine and so distributed throughout the fiber that it is difficult todistinguishably recognize the individual voids under observation by anoptical microscope in bright field illumination, the whole fiber havinga glimmering aspect when observed by an optical microscope under darkfield illumination, said fiber containing in the voids at least onesubstance selected from the group consisting of dyestuifs, theirintermediates, light-stabilizers, heatstabilizers, surfactants,softeners, flame resistors, antistatic agents, mordanting agents,polymerizable compounds, solvents and water, which comprises absorbingthe said substance into the said fiber.

3. A method for preparing a melt-spun structured polypropylene fiberhaving numberless ultra-fine voids distributed throughout the fiber andhaving an initial solvent absorbency greater than 25%, said voids beingso fine and so distributed throughout the fiber that it is difiicult todistinguishably recognize the individual voids under observation by anoptical microscope in bright field illumination, the whole fiber havinga glimmering aspect when observed by an optical microscope under darkfield illumination, said fiber containing in said voids a substance ofhigh molecular weight synthesizable from reactants of lower molecularweight, which comprises impregnating the fiber with said reactants inamount suflicient to fill said voids, and then subjecting the fiber toconditions which result in reaction between said reactants, whereby saidsubstance of high molecular weight is formed in situ in said voids.

4. A method according to claim 3, wherein said reactants comprise adiazo component and a coupling compound, whereby a dyestuif of highermolecular weight is produced in situ in said voids.

5. A method for after-treating the structured polypropylene fibers ofclaim 1, which comprises subjecting the fibers containing thesubstance(s) to a treatment'for reducing, diminishing or substantiallydissipating the said voids.

6. A method as claimed in claim 5, in which the treatment is carried outby contacting the fibers with a vapor of an organic solvent which iscapable of swelling or plasticizing polypropylene.

7. A method as claimed in claim 5, in which the treatment is carried outby impregnating the fibers with an organic solvent which is capable ofswelling or plasticizing polypropylene and then gradually evaporatingthe solvent.

8. A method as claimed in claim 5, in which the treat ment is carriedout by heating the fibers at a temperature of from 120 C. to 160 C. andin substantial absence of a solvent for the polypropylene.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTSBelgium. Great Britain.

15 NORMAN G. TORCHIN, Primary Examiner.

2. A METHOD FOR PREPARING A MELT-SPUN STRUCTURED POLYPROPYLENE FIBERHAVING NUMBERLESS ULTRA-FINE VOIDS DISTRIBUTED THROUGHOUT THE FIBER ANDHAVING AN INITIAL SOLVENT ABSORBENCY GREATER THAN 25%, SAID VOIDS BEINGSO FINE AND SO DISTRIBUTED THROUGHOUT THE FIBER THAT IT IS DIFFICULT TODISTINGUISHABLY RECOGNIZE THE INDIVIDUAL VOIDS UNDER OBSERVATION BY ANOPTICAL MICROSCOPE IN BRIGHT FIELD ILLUMINATION, THE WHOLE FIBER HAVINGA GLIMMERING ASPECT WHEN OBSERVED BY AN OPTICAL MICROSCOPE UNDER DARKFIELD ILLUMINATION, SAID FIBER CONTAINING IN THE VOIDS AT LEAST ONESUBSTANCE SELECTED FROM THE GROUP CONSISTING OF DYESTUFFS, THEIRINTERMEDIATES, LIGHT-STABILIZERS, HEATSTABILIZERS, SURFACTANTS,SOFTENERS, FLAME RESISTORS, ANTISTATIC AGENTS, MORDANTING AGENTS,POLYMERIZABLE COMPOUNDS, SOLVENTS AND WATER, WHICH COMPRISES ABSORGINGTHE SAID SUBSTANCE INTO THE SAID FIBER.